Wafer sheet with adhesive on both sides and attached semiconductor wafer

ABSTRACT

Providing a method for die bonding semiconductor elements surely without causing damage thereto in a shorter time with less steps of operations, thereby improving the productivity. 
     A semiconductor wafer  1  of which back side is laminated onto a wafer sheet  2  covered with thermosetting adhesive layers  43  on both sides thereof is diced, the wafer sheet  2  is expanded to expand the separation groove  41  with the semiconductor elements  3  positioned on die pads  30  while being separated from each other under the condition that the separation groove  41  is expanded, a die bonding head  4  equipped with a compressed air passage  5  and a cutting blade  6  is lowered to cut off the wafer sheet  2  below the expanded separation groove by means of the cutting blade  6  thereby separating the semiconductor elements into individual devices, and compressed air is let out of the compressed air passage  5  to press the semiconductor element  3  thereby bonding the thermosetting adhesive layer  43  of the wafer sheet  2  onto the surface of the die pad  30.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wafer sheet, a method of producing asemiconductor device using the wafer sheet and an apparatus forproducing a semiconductor device. More particularly, it relates to asemiconductor wafer laminated on its back side to a wafer sheet which iscovered by thermosetting adhesive layers on both sides, while elementseparation and die bonding operations are carried out substantiallysimultaneously, thereby improving the productivity, a method ofproducing a semiconductor device using the wafer sheet and an apparatusfor producing a semiconductor device.

2. Description of the Related Art

Steps for producing semiconductor devices include a bonding step. Thebonding step comprises a die bonding step where each of semiconductorelements (dice) which have been separated from a wafer is bonded onto adie pad and a wire bonding step where electrodes on the semiconductorelement 3 and inner leads are electrically connected with each other bymeans of thin metal wires.

As the wire bonding operation, among the operations in the bonding step,has been increasingly automated, it has become relatively more importantto rationalize the feeding of semiconductor elements around a diebonder. As a result, various methods of feeding the semiconductorelements, such as a direct pickup system, have recently been devised bymanufacturers and have been disseminating.

FIGS. 10A, 10B are schematic diagrams showing a die bonding apparatuswith the direct pickup system of the prior art, where FIG. 10A is aperspective view and FIG. 10B is a cross sectional view of a keyportion.

As shown in the drawing, while locating the semiconductor element 3attached to the wafer sheet 2, only good elements are thrust up by athrust pin 38, picked up by a suction head 39, moved onto a die pad 30of a lead frame 29 and bonded thereon. Good elements may be identifiedeither by using an ink mark provided on the surface of a defectiveelement or by means of a map of good elements stored on a floppy disk(not shown and hereinafter referred to as F/D) which provides theinformation on the positions of good elements.

However, either of the methods described above has such problems that,since the selected elements are thrust up by the thrust pin 38, pickedup by the suction head 39, moved onto the die pad 30 which is located ata distance and bonded thereon, there is a possibility that thesemiconductor element 3 is damaged during thrusting, picking up or diebonding, and the throughput decreases due to longer time required forthe bonding step as a whole. In an attempt to solve the problems of theprior art, for example, Japanese Patent Laid-Open Publication No. Hei.6-204267 discloses a semiconductor wafer having an adhesive tapeattached on the front side thereof is diced on the back side thereof andeach of the separated semiconductor elements is bonded on the back sideto a element mounting position of a lead frame by pressing on the frontsurface of the semiconductor element via the adhesive tape using a diebonding fixture, and the adhesive tape is removed and the semiconductorelement is bonded on the back side to the element mounting position in asingle step.

However, with the die bonding step described above, although theadhesive tape is attached to the front surface of the semiconductorwafer, possibility of damaging the integrated circuit due to mechanicalimpact cannot be eliminated because the front surface of thesemiconductor element the integrated circuit is formed is pressed viathe adhesive tape by the die bonding fixture. Further, since theadhesive tape is attached to the front surface of the semiconductorwafer, an adhesive material sticks onto the surface of electrodesprovided on the front surface of the wafer thereby causing contaminationand, wire bonding of thin metal wires thereon without cleaning mayresult in poor reliability of connection. To solve this problem, it isrequired to introduce a new process of cleaning the electrode surface.

SUMMARY OF THE INVENTION

The present invention has been attained to solve the problems of the diebonding method of the prior art as described above, and an object of thepresent invention is to provide a wafer sheet surely carrying out diebonding with power steps without causing damage to the semiconductorelements, thereby improving productivity, a method of producing asemiconductor device using the wafer sheet, and a semiconductorproducing apparatus.

The wafer sheet according to the present invention comprises anexpandable resin sheet with thermosetting adhesive layers formed on bothsides and, a semiconductor wafer attached to the back side thereofbefore dicing.

The present invention also provides a wafer sheet wherein the expandableresin sheet is made of soft vinyl chloride. Further the presentinvention provides a wafer sheet wherein the expandable resin sheet ismade of a polyimide-modified epoxy resin containing 40% by weight of asilver filler.

Further the present invention provides a wafer sheet wherein theexpandable resin sheet is made of an electrically conductive sheet withelectrically conductive thermosetting adhesive layers formed on bothsides thereof.

The present invention also provides a wafer sheet wherein the expandableresin sheet has multitude of through holes.

The method of producing the semiconductor devices according to thepresent invention comprises the steps of bonding one side of the wafersheet made from the expandable resin sheet with thermosetting adhesivelayers formed on both sides thereof laminated onto the back side of thesemiconductor wafer, and dividing the semiconductor wafer into aplurality of semiconductor elements by dicing; expanding the wafer sheetwhich carries the separated semiconductor elements being laminatedthereon, thereby widening the separation grooves between thesemiconductor elements; positioning proper one among the semiconductorelements on a die pad of a lead frame whereon the element is to bedie-bonded while being separated from each other; and cutting off thewafer sheet below the expanded separation grooves surrounding thesemiconductor elements which have been positioned on the die padsthereby separating the piece of wafer sheet with the semiconductorelement laminated thereon, and pressing the adhesive surface on the sideof the wafer sheet, opposite to that where the semiconductor element isattached, onto the die pad surface.

The present invention also provides a method wherein the separatedsemiconductor element is pressed by means of compressed air therebypressing the adhesive surface on the side of the wafer sheet opposite tothat where the semiconductor element is attached onto the die padsurface.

The semiconductor device producing apparatus of the present inventioncomprises a stage whereon a wafer sheet carrier, which holds the wafersheet with the semiconductor elements laminated thereon while beingseparated from each other, is placed at a distance from the lead frame;a die bonding means which is disposed at a die bonding position of thestage to be capable of moving vertically and has a hollow space to coverthe semiconductor element while keeping a specified clearance during diebonding, a die bonding head having a compressed air passage opening atthe bottom of the hollow space and a cutting blade for cutting off thewafer sheet below the expanded separation grooves between thesemiconductor elements provided at the tip of the die bonding head and adrive section for driving the die bonding head; and a compressed airsupplying means for supplying compressed air into the compressed airpassage during die bonding of the semiconductor element.

The present invention also provides a semiconductor device producingapparatus wherein the cutting blade is disposed to be inserted throughthe expanded separation grooves with a specified clearance kept from theside faces of the grooves surrounding the semiconductor element to bedie-bonded, in such a way that the cutting blade can be attached to thetip of the die bonding head and removed therefrom.

The present invention also provides a semiconductor device producingapparatus provided with X-/Y-axis direction drive means for moving thestage in X- and Y-axis directions thereby to move a proper element amongthe semiconductor elements, which have been separated from each other,onto a die pad of the lead frame whereon the element is to be die-bondedand setting the element thereon, and element rotating means for rotatingthe wafer sheet carrier placed on the stage thereby to adjust theinclination angle of the semiconductor element at the setting positionthereof.

Also according to the present invention, the semiconductor deviceproducing apparatus has the compressed air passage of the die bondinghead disposed on the vertical line passing through the center of thesemiconductor element to be die-bonded, a semiconductor layer disposedon the die bonding head to emit a light beam in the vertical directiontoward the semiconductor element surface, a element position detectingmeans for locating the point on the semiconductor element surface whichis irradiated by the laser beam emitted by the semiconductor laser andgenerating a position signal to indicate deviation of the semiconductorelement from the normal position in the X-axis and Y-axis directionswith zero position being set at the laser spot and the information onthe inclination angle from the normal direction, and a die bondingcontroller which, upon receipt of the position signal from the elementposition detecting means, sends correction signals for the displacementor inclination angle to the X-/Y-axis direction drive means or theelement rotating means and, when the position of the semiconductorelement is corrected, sends an operation command signal to the diebonding means and the compressed air supplying means to start thespecified operations.

The present invention, having the constitution described above, has sucheffects as described below.

Since the wafer sheet is made from the expandable resin sheet withthermosetting adhesive layers formed on both sides thereof, thesemiconductor elements laminated on the wafer sheet can be separatedinto individual elements and die-bonded substantially at the same timeduring dicing.

By using the soft vinyl chloride for the expandable resin sheet,low-cost wafer sheet can be obtained.

By using the expandable resin sheet made of a polyimide-modified epoxyresin containing 40% by weight of a silver filler, the wafer sheethaving good heat conductivity can be obtained without significantlyaffecting the stretching capability.

Since both the expandable resin sheet and the thermosetting adhesivelayers formed on both sides thereof are made of electrically conductivematerials, the wafer sheet is capable of accommodating the semiconductorelement which requires it to make the potential of the back surface ofthe semiconductor element equal to the ground level.

Since the expandable resin sheet has multitude of through holes, theresin sheet is capable of stretching more, and therefore wider expandedseparation groove can be obtained during expansion of the wafer sheet,thus making it possible to insert the cutting blade of the die bondinghead into the expanded separation groove with a greater margin andmaking it easier to separate the semiconductor elements into individualdevices.

Further, since the back side of the semiconductor wafer element islaminated onto one of the adhesive layers of the wafer sheet and, afterexpanding the separation grooves made by dicing, the wafer sheet belowthe expanded separation groove is cut off thereby separating thesemiconductor elements into individual devices while the semiconductorelement is pressurized to have the other adhesive surface of the wafersheet laminated onto the die pad surface, the semiconductor element canbe die-bonded with less number of steps and the productivity isimproved.

Also since the semiconductor element is pressed by compressed air duringdie bonding, there is no possibility of causing mechanical damage to thesemiconductor element.

Further, since the semiconductor device producing apparatus is made in acompact configuration comprising the stage whereon the wafer sheet isplaced, the die bonding means having the compressed air passage, thecutting blade which cuts off the wafer sheet below the expandedseparation groove between the semiconductor elements and the compressedair supplying means which supplies compressed air to the compressed airpassage, the compact semiconductor device producing apparatus can beprovided at a low cost wherein separation of the semiconductor elementsinto individual devices and die bonding operation can be carried outsubstantially at the same place and substantially at the same time.

Also since the cutting blade which cuts off the wafer sheet below theexpanded separation groove is made in a size corresponding to the sizeof the semiconductor device to be die-bonded is provided to be attachedto and detached from the bonding head, different kinds of thesemiconductor device can be accommodated very easily and quickly.

Further, since the X-/Y-axis direction drive means of the stage whereonthe wafer sheet carrier is placed and the element rotating means areprovided, displacement and inclination of the semiconductor element tobe die-bonded can be easily corrected.

Also since the semiconductor producing apparatus is made in such aconfiguration that is provided with the element position detecting meanswhich issues the position signal representing the displacement andinclination in the setting position of the semiconductor element to bedie-bonded, and the die bonding controller which issues the correctionsignal based on the position signal to control the X-/Y-axis directiondrive means and the element rotating means of the stage whereon thewafer sheet carrier is placed, the semiconductor element remaining onthe wafer sheet can be easily moved to the normal bonding position bycorrecting the displacement and inclination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1F are schematic diagrams showing a flow sheet up to a diebonding step in the order of carrying out the first embodiment of thepresent invention.

FIG. 2 is a plan view showing a wafer sheet carrier made in theexpansion step according to the first embodiment of the presentinvention.

FIG. 3 is a cross sectional view taken along line III—III of FIG. 2.

FIG. 4 is a perspective view schematically showing the configuration ofthe die bonding apparatus according to the first embodiment of thepresent invention.

FIG. 5 is a flow chart showing the order of operations of the diebonding apparatus according to the first embodiment of the presentinvention.

FIGS. 6A-6C are schematic diagrams showing the procedures of operationsto correct improper position of the semiconductor element to bedie-bonded on the die bonding apparatus according to the firstembodiment of the present invention.

FIG. 7 is a plan view showing the perforated wafer sheet according tothe second embodiment of the present invention.

FIG. 8 is a partially cutaway side view showing the configuration of thedie bonding head of the die bonding apparatus according to the thirdembodiment of the present invention.

FIG. 9 is a bottom view of FIG. 8.

FIGS. 10A and 10B are perspective views schematically showing the diebonding apparatus of the direct pick-up system of the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment 1

Now a first embodiment of the present invention will be described belowwith reference to the accompanying drawings.

FIGS. 1A through 1F show the producing steps up to the die bonding stepin the order of carrying out the first embodiment of the presentinvention, wherein the steps are as follows.

(A) Wafer Sheet Attaching Step (FIG. 1A)

A semiconductor wafer 1 is attached on the back side thereof to one sideof a wafer sheet 2 comprising a tape made of soft vinyl chloride havinga thickness of 80 to 120 μm with thermosetting adhesive layers 43 onboth sides thereof. The soft vinyl chloride tape is a low-cost materialcapable of stretching substantially and is suited for the expansionstep. A wafer test is conducted to determine whether the integratedcircuit on the semiconductor wafer 1 is normally functional or not, withthe result being stored in the form of a map of good elements on an F/D(not shown).

(B) Wafer Dicing Step (FIG. 1B)

Separation grooves 41 are formed along borders of the individualelements by means of a dicing saw thereby cutting the semiconductorwafer 1 into individual semiconductor elements 3 while leaving the wafersheet 2 intact.

(C) Expansion Step (FIG. 1C)

The wafer sheet 2 is stretched and held on a support ring (not shown) bymeans of a band to prepare a wafer sheet carrier (both not shown). Thusthe separation grooves 41 between the semiconductor elements 3 areexpanded to about 1.5 to 2.0 mm, for example, into expanded separationgrooves 42.

(D) Positioning Step (FIG. 1D)

The wafer sheet carrier is set on the stage of a movable base (both notshown) of the die bonding apparatus, whereon with the distance betweenthe wafer sheet 2 and the lead frame 29 is about 2 to 3 mm, for example,the semiconductor elements 3 to be die-bonded are positioned on the diepads 30 while being separated from each other, using a semiconductorlaser 12, a CCD camera 13, the X-/Y-axis direction drive means and anelement rotating means (both not shown). The die pads 30 are pre-heatedto a temperature from 50 to 80° C. by means of a heat block 34 disposedbelow.

(E) Separation Step (FIG. 1E)

A die bonding head 4 is lowered to cover the semiconductor element 3 ina hollow space 7 thereof, and a cutting blade 6 mounted on the tip ofthe die bonding head is inserted into the expanded separation grooves 42between the separated semiconductor elements 3 thereby cutting the wafersheet 2 and separating the individual semiconductor elements 3. In thisprocess, the inner surface of the hollow space 7 does not make contactwith the semiconductor element 3 at all and the edge of the cuttingblade 6 does not reach the lead frame 29.

(F) Die Bonding Step (FIG. 1F)

Compressed air is let out of the compressed air passage 5 of the diebonding head 4 substantially at the same time the semiconductor elements3 to be die-bonded are separated into individual elements, thereby topress the surface of the semiconductor element 3 so that the adhesivesurface of the wafer sheet on the side opposite to that of thesemiconductor element is laminated onto the die pad 30. Then the heatblock 34 is heated to a temperature from 150 to 250° C., for example,thereby to heat and harden the thermosetting adhesive layer 43. Arrowmarks in and outside the compressed air passage 5 indicate thedirections of compressed air flow.

As described above, since the operations of separating the semiconductorelements and die bonding are carried out substantially at the same timeand reliably, the number of steps required before the die bonding stepis reduced and the productivity is improved.

Also because the semiconductor elements 3 are separated into individualelements by cutting off the wafer sheet 2 while being separated from thelead frame 29 and the semiconductor element 3 is die-bonded onto the diepad 30 by applying pressure by means of compressed air, mechanical forceis not applied to the semiconductor elements 3 thus eliminating thepossibility of causing damage thereto. Also the cutting blade 6 nevercuts the lead frame 29.

FIG. 2 is a plan view showing the wafer sheet carrier made in theexpansion step, and FIG. 3 is a cross sectional view taken along linesIII—III. As can be seen in the drawing, the wafer sheet carrier 15 has aconfiguration so that the wafer sheet 2 with the separated semiconductorelements 3 bonded thereto is stretched toward the outside of the supportring 16 and is secured in a groove made in an outer side face of thesupport ring 16 by means of the band 17. The wafer sheet carrier is seton the stage 22 a of the movable base of the die bonding apparatus insuch a positional relationship with fixed rollers 18 a, 18 b, a movableroller 19 and the lead frame 29 as shown in FIGS. 2 and 3, so that thefollowing steps (positioning step, separation step and die bonding step)are carried out with this setup.

Now the configuration of the die bonding apparatus which carries out thesteps (A) through (F) will be described below.

FIG. 4 is a perspective view schematically showing the configuration ofthe die bonding apparatus according to the present invention. As can beseen in the drawing, the movable base 22 which has the stage 22 awhereon the wafer sheet carrier 15 is placed has a fixed portion 22 bwhich is fixed on a Y-axis motion table 23 which can move in the Y-axisdirection, the Y-axis motion table 23 is disposed to be movable on aguide of an X-axis motion table 25 which can move in the X-axisdirection and the X-axis motion table 25 is disposed to be movable on aguide of a fixed base 27. The movable base 22 and the Y-axis motiontable 23 are made movable in the Y-axis direction by means of a Y-axisdrive motor 24 equipped with a ball screw mounted on the X-axis motiontable 25, and the X-axis motion table 25 is made movable in the X-axisdirection by means of an X-axis drive motor 26 equipped with a ballscrew mounted on the fixed base 27. The Y-axis motion table 23, theY-axis drive motor 24, the X-axis motion table 25, X-axis drive motor 26and the fixed base 27 constitute the X-/Y-axis direction drive means 28,which moves the semiconductor element 3 to the die bonding position. Thestage 22 a of the movable base 22 has the fixed rollers 18 a, 18 b andthe movable roller 19 made of Teflon disposed at angular intervals of120 degrees for positioning the wafer sheet carrier 15 to be placedthereon into a specified position and rotating the wafer sheet carrier15, so that the periphery of the wafer sheet carrier 15 is rotated by aroller drive motor 20 linked to the fixed roller 18 b. When the wafersheet carrier 15 is fed from a wafer sheet carrier housing case 33 ontothe stage 22 a, the movable roller 19 temporarily retracts to a safeposition to give way for the feeding operation and, after feeding,returns to the normal position to make contact with the periphery of thewafer sheet carrier 15 while pressing lightly thereto (not shown).Applied to a position of the stage 22 a is a coating of Teflon so thatthe adhesive material of the wafer sheet 2 does not impede the rotation.The fixed rollers 18 a, 18 b, the movable roller 19 and the roller drivemotor 20 constitute the element rotating means 21, which rotates thewafer sheet carrier 15 thereby to correct the inclination of thesemiconductor element 3.

Disposed above the die bonding position of the wafer sheet carrier 15 isthe die bonding head 4 which moves in the vertical direction as shown inFIG. 1, the die bonding head 4 has the hollow space 7 (not shown in FIG.4) which covers the semiconductor element 3 to be die-bonded with aspecified clearance and the compressed air passage 5 which opens at thebottom of the hollow space 7, and the cutting blade 6 mounted at the tipthereof to cut the wafer sheet 2 along the expanded separation grooves42 which surround the semiconductor element 3 to be die-bonded, the diebonding head 4 is moved vertically by a drive element (not shown). Thecompressed air passage 5 and the compressed air generator 9 areconnected by a flexible tube 10 for supplying compressed air during diebonding. The die bonding head 4 and the drive element constitute the diebonding means 8, while the compressed air generator 9 and the flexibletube 10 constitute the compressed air supplying means 11. Once thesemiconductor element 3 to be die-bonded is set at the die bondingposition in accordance to the position information of good elementsstored on the F/D 32, the semiconductor laser 12 operates to direct alaser beam to a point F on the surface of the semiconductor element 3.The laser beam spot is captured by the CCD camera 13, so that positionsignal of the semiconductor element 3 with reference to the laser spot Fis sent from the CCD camera 13 to the die bonding controller 31. Thesemiconductor laser 12 and the CCD camera 13 constitute the elementposition detecting means. The die bonding controller 31 determineswhether the semiconductor element 3 is set at the correct positionaccording to the position signal which has been received. When theposition is not correct, the die bonding controller 31 sends correctionsignal to the roller drive motor 20, the Y-axis drive motor 24 or theX-axis drive motor 26 thereby to correct the setting position of thesemiconductor element 3, then sends the operation command signal to thecompressed air supplying means 11 thereby to carry out the die bondingoperation. Inward and outward arrows to and from the die bondingcontroller 31 indicate the directions of information flow.

Now the die bonding method with the die bonding apparatus will bedescribed in detail below.

FIG. 5 is a flow chart showing the procedure of the operations of thedie bonding apparatus, and FIG. 6 shows the procedure of correctingimproper position of the semiconductor element to be die bonded.

First, the die bonding controller 31 sends a temporary element settingcommand signal for moving the wafer sheet carrier 15 in the X-axis andY-axis directions in order to set the semiconductor element 3 to bedie-bonded at the die bonding position according to the mappinginformation of the good elements stored in the F/D 32 (S1). Upon receiptof the temporary element setting command signal, the Y-axis drive motor24 and the X-axis drive motor 26 move the Y-axis motion table 23 and theX-axis motion table 25 according to the temporary element settingcommand signal, thereby to temporarily set the semiconductor element 3supported by the wafer sheet carrier 15 placed on the stage 22 a of themovable base 22 to the die bonding position (S2) This causes thesemiconductor laser 12 to direct the laser beam to the center of the diebonding position thereby to irradiate the point F on the surface of thesemiconductor element 3. The CCD camera 13 captures the image of thebeam spot at the point F and sends coordinate position information P₁(x₁, y₁) and P₂ (x₂, y₂) of two corners, which take the point F as theorigin, to the die bonding controller 31 (S3, FIG. 6A). The die bondingcontroller 31 calculates, from the coordinate position information P₁(x₁, y₁) and P₂ (x₂, Y₂), gradient M of an edge L of the semiconductorelement 3 by equation (1), inclination angle Θ with respect to the Xaxis by equation (2) and inclination angle A with respect to the Y axisby equation (3), and sends an angle correction signal to the rollerdrive motor 20 to make it rotate the wafer sheet carrier 15 by the angleA counter-clockwise in the case of a positive gradient or clockwise inthe case of a negative gradient (S4).

M=(y ₁ -y ₂)/(x ₁ -x ₂)  (1)

Θ=tan⁻¹|(y ₁ -y ₂)/(x ₁ -x ₂)|  (2)

A=90 −Θ  (3)

Upon receipt of the angle correction signal, the roller drive motor 20rotates the wafer sheet carrier 15 by the angle A in the specifieddirection via the fixed roller 18 b according to the signal, thereby tocorrect the inclination of the semiconductor element 3 (S5). Then theCCD camera 13 captures the coordinate position information P₁ (x₁, y₁)and P₂ (x₂, y₂) of two corners which have been corrected similarly tothat described above and sends them to the die bonding controller 31(S6). The die bonding controller 31 determines whether the inclinationangle A of the semiconductor element 3 with respect to the Y-axis iswithin tolerance or not based on the coordinate position information P₁(x₁, y₁) and P₂ (x₂, y₂) which have been received. When it is out of thetolerance, a similar correcting operation is repeated, and the stepproceeds to the next step when it is within the tolerance (S7).

Then the CCD camera 13 captures coordinate position information P₃ (x₃,y₃) of a corner taking reference to the point F as the origin and sendsthe signal to the die bonding controller 31 (S8, FIG. 6B). The diebonding controller 31 compares the coordinate position information P₃(x₃, y₃) and correct coordinates P_(n) (x_(n), y_(n)) stored in memory,calculates displacements of the semiconductor element 3 in X-axis andY-axis directions by equations (4) and (5), and sends positioncorrection signals to the Y-axis drive motor 24 and the X-axis drivemotor 26 (S9).

Δx=x _(n) −x ₃  (4)

Δy=y _(n) −y ₃  (5)

Upon receipt of the position correction signal, the Y-axis drive motor24 and the X-axis drive motor 26 move the Y-axis motion table 23 and theX-axis motion table 25 by Δ x and Δ y thereby to correct thedisplacement of the semiconductor element 3 (S10, FIG. 6C). Then the CCDcamera 13 captures the corrected coordinate position information P₃ (x₃,y₃) of the corner and sends the signal to the die bonding controller 31(S11).

The die bonding controller 31 determines whether the displacements ofthe semiconductor element 3 in X-axis and Y-axis directions are withintolerance or not based on the coordinate position information P₃ (x₃,y₃) which have been received. When it is out of the tolerance, acorrecting operation similar to that described above is repeated, andthe step proceeds to the next step when it is within the tolerance(S12).

Then the die bonding controller 31 issues the operation command signalto the die bonding means 8 (S13). The die bonding means lowers thebonding head 4 to a specified position according to the command signal,so that the cutting blade 6 disposed at the tip thereof cuts the wafersheet 2 in the expanded separation groove 42 surrounding thesemiconductor element 3 thereby separating the individual elements(S14). Substantially at the same time, the die bonding controller 31issues the operation command signal to the compressed air supplyingmeans 11 (S15). Compressed air is blasted through the flexible tube 10and the compressed air passage 5 into the hollow space 7 of the bondinghead 4, so that the semiconductor element 3 is pressed by the compressedair and the adhesive surface of the wafer sheet 2 on the side oppositeto that of the semiconductor element 3 and adheres the die pad 30 to bedie-bonded (S16). As the die pad 30 is heated by the heat block 34, thethermosetting adhesive layer 43 is heated to harden, thereby completingthe die bonding operation (S17).

Although the wafer sheet 2 is made by using soft vinyl chloride as thebase material in the first embodiment, the wafer sheet may also be madeof, for example, a polyimide-modified epoxy resin containing 40% byweight of a silver filler having a thickness of 80 to 120 μm, in orderto improve the heat conductivity between the semiconductor element 3 andthe die pad 30. In this case, a sheet having good heat conductivity canbe obtained while maintaining sufficient elasticity. Also the sheet maybe made capable of stretching more by including a multitude of throughholes 36 having diameter of 0.2 mm at intervals of 0.3 to 0.5 mm thereinas shown in FIG. 7 of the second embodiment.

Embodiment 2

FIG. 7 is a plan view of a perforated wafer sheet according to thesecond embodiment of the present invention. The perforated wafer sheet35 is made of a polyimide-modified epoxy resin containing at least 80%by weight of a silver filler to make it electrically conductive and isformed into a film having a thickness of 80 to 120 μm, with a multitudeof through holes 36 having a diameter of, for example, 0.2 mm madetherein at intervals of 0.3 to 0.5 mm to make it capable of stretchingmore, and is covered on both sides thereof by electrically conductivethermosetting resin adhesive layers 43 containing 70% by weight of asilver filler. The content of the silver filler is set in considerationof facts that a resin sheet shows sufficient electrical conductivitywith a silver filler content of about 80% by weight, and a resin pasteshows sufficient electrical conductivity with a silver filler content ofabout 70% by weight.

The die bonding step with the perforated wafer sheet 35 is exactly thesame as that of the first embodiment.

Making the perforated wafer sheet 35 electrically conductive results insuch effects as the operation of die-bonding the semiconductor elementwhen the potential of the back surface of the semiconductor element mustbe equal to the ground level with higher reliability with fewer steps,thereby improving the productivity.

Embodiment 3

FIGS. 8 and 9 show the configuration of the die bonding head of the diebonding apparatus according to the third embodiment of the presentinvention, FIG. 8 being a partially cutaway side view and FIG. 9 being abottom view of FIG. 8. As shown in the drawing, a blade attachment 37having the cutting blade 6 is attached to the tip of the bonding head 4by means of set screws 38, the cutting blade 6 being formed in such aconfiguration as can be inserted into the expanded separation groove 42of the semiconductor element 3 to be die-bonded with a specifiedclearance. Since the blade attachment 37 having the cutting blade 6corresponding to the size of the semiconductor element 3 to bedie-bonded is provided to be attached to and detached from the tip ofthe bonding head 4, different kinds of semiconductor elements can beaccommodated very easily and quickly.

What is claimed is:
 1. A wafer sheet comprising an elastic, stretchableresin sheet having opposed first and second sides and a thermosettingadhesive layer disposed on both of the first and second sides of theresin sheet, and a semiconductor wafer having a front side includingintegrated circuit elements and a back side opposite the front side, thesemiconductor wafer being attached at the back side to the first side ofthe elastic, stretchable resin sheet before dicing of the semiconductorwafer.
 2. The wafer sheet according to claim 1, wherein the elastic,stretchable resin sheet is soft vinyl chloride.
 3. The wafer sheetaccording to claim 1, wherein the elastic, stretchable resin sheet is apolyimide-modified epoxy resin containing 40% by weight of a silverfiller.
 4. The wafer sheet according to claim 1, wherein the elastic,stretchable resin sheet and the thermosetting adhesive layers on thefirst and second sides of the elastic, stretchable resin sheet areelectrically conductive.
 5. The wafer sheet according to claim 1,wherein the elastic, stretchable resin sheet has plurality of throughholes.
 6. A wafer sheet comprising an elastic, stretchable resin sheethaving opposed first and second sides and a thermosetting adhesive layerdisposed on both of the first and second sides of the elastic,stretchable resin sheet, so that a semiconductor wafer, having a frontside including integrated circuit elements and a back side opposite thefront side, may be attached at the back side to the first side of theelastic, stretchable resin sheet before dicing of the semiconductorwafer.
 7. The wafer sheet according to claim 6, wherein the elastic,stretchable resin sheet is soft vinyl chloride.
 8. The wafer sheetaccording to claim 6, wherein the elastic, stretchable resin sheet is apolyimide-modified epoxy resin containing forty percent by weight of asilver filler.
 9. The wafer sheet according to claim 6, wherein theelastic, stretchable resin sheet and the thermosetting adhesive layerson the first and second sides of the elastic, stretchable resin sheetare electrically conductive.
 10. The wafer sheet according to claim 6,wherein the elastic, stretchable resin sheet has a plurality of throughholes.